1. Technical Field
The present invention relates to an organic light emitting device and a method for fabricating the same.
2. Related Art
Among flat panel display devices, light emitting device has an advantage in that it has high response speed and low power consumption. The light emitting device can also be manufactured thin in size and light in weight because of not requiring backlights.
In particularly, organic light emitting device has an organic light emitting layer between an anode and a cathode. Holes from the anode and electrons from the cathode are combined within the organic light emitting layer to create hole-electron pairs, i.e., excitons. The organic light emitting device emits lights by energy generated while the excitons return to ground state.
The organic light emitting device comprises a plurality of sub-pixels which have red, green, and blue emission layers to display full colored images. And, barrier ribs can be used to form red, green, or blue emission layer in each sub-pixel.
FIG. 1A is a cross sectional view of an organic light emitting device according to a prior art.
Referring to FIG. 1A, a light emitting diode 190 comprising a first electrode 150, an emission layer 180, and a second electrode 185 is disposed on a substrate 140.
The first electrode 150 may be an anode, and may be deposited with a transparent conductive film such as Indium Tin Oxide and then be patterned in the form of multiple stripes.
An insulating layer 160 is disposed on the first electrode 150, which comprises an opening 165 for exposing the first electrode 150, and a barrier rib 170 is disposed on the insulating layer 160 in the form of an overhang. The emission layer 180 is disposed in the opening 165 and a second electrode 185 is disposed on the emission layer 180. The emission layer 180 and the second electrode 185 are patterned by the barrier rib 170 having the form of an overhang.
FIG. 1B is a cross sectional view of an organic light emitting device according to another prior art.
Referring to FIG. 1B, a thin film transistor T comprising a semiconductor layer 105, a gate insulating layer 110, a gate electrode 115, a inter-insulating layer 120, a source electrode and a drain electrode 125a, 125b is disposed on a first substrate 100.
A second substrate 140 is located to oppose the first substrate 100. A light emitting diode 190 comprising a first electrode 150, an emission layer 180, and a second electrode 185 is disposed on the second substrate 140.
The first electrode 150 may be an anode, and the first electrode 150 may be a common electrode which is substantially formed on a full surface of the second substrate 140. The first electrode 150 may comprise a transparent conductive material such as Indium Tin Oxide. An insulating layer 160 is disposed on the first electrode 150, which comprises openings 165 for exposing the first electrode 150, and barrier ribs 170 are disposed on the insulating layer 160 in the form of an overhang. The emission layers 180 are disposed in the openings 165 and second electrodes 185 are disposed on the emission layers 180. The emission layers 180 and the second electrodes 185 are patterned by the barrier rib 170 having the form of an overhang.
When the first substrate 100 and the second substrate 140 are attached to each other, a drain electrode 125b of the first substrate 100 and the second electrode 190 of the second substrate 140 are electrically connected to each other by a metal line 195. Accordingly, the light emitting diode 190 provided on the second substrate 140 can be driven by the thin film transistor of the first substrate 100. The aforementioned construction allows for an inverted-OLED in which the first electrode 150 is comprise a transparent conductive material, and has an advantage in providing high transmittance as a device of top emission type.
The thusly constructed organic light emitting device is driven when prescribed electrical signals are applied to the first and second electrodes through wiring or thin film transistor to thereby display images.
However, this organic light emitting device has provided the first electrode in the form of a stripe or full surface electrode using a transparent conductive film such as an ITO film which has a high work function. Accordingly, the sheet resistance of the first electrode increased and the transmission of signals to each pixel was delayed. In particular, the transmission of signals was severely delayed in case of large-area light emitting devices and thus desired images could not be displayed.